This application claims the priority of Korean Patent Application No. 10-2004-0004441, filed on Jan. 20, 2004, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a field emission type backlight device, and more particularly to a field emission type backlight device for a liquid crystal display (LCD) apparatus.
2. Description of the Related Art
An LCD apparatus has a backlight device in a rear side which typically supplies a white light. A cold cathode tube has been commonly used as a backlight device. Flat panel backlight devices, however, are required for thinner LCD apparatuses.
FIG. 1 is a sectional view showing a configuration of a conventional backlight device for the LCD apparatus.
A spacer (not shown) is provided between a front substrate 1 and a rear substrate 4. The space between the front substrate 1 and the rear substrate 4 is sealed with a wall (not shown). A cathode electrode 5 is provided in plane or stripe on the rear substrate 4. A field emission source such as a carbon nanotube (CNT) 6 is provided on the cathode electrode 5. On the front substrate 1 is an anode electrode 2, which is generally a transparent electrode. A light-emitting material 3 (which may be a fluorescent material) is deposited on the anode electrode 2.
When a predetermined voltage is applied between the cathode electrode 5 and the anode electrode 2, electrons are emitted from the field emission source 6 to excite the light-emitting layer 3. Light from the light-emitting layer 3 is incident on the LCD apparatus through the light-emitting layer 3, the anode electrode 2, and the front substrate 1.
A conventional flat panel backlight device can have non-uniform luminance because of a concentration of electron emission in the edge of the cathode electrode 5. In addition, since light is to be supplied to the LCD apparatus through the light-emitting layer 3 and the front substrate 1, light transmittance can be reduced due to the light-emitting layer 3. The bigger the LCD apparatus grows large in size, the bigger the non-uniformity in luminance.
There is a field emission device with good energy efficiency. For instance, in U.S. Pat. No. 5,760,858, a triode-structure field emission device is combined with a liquid crystal panel, so that it is possible to obtain a low power consuming backlight. In addition, it is possible to obtain uniform high luminance because the field emission device is in a surface emission mode.
However, the backlight device described in U.S. Pat. No. 5,760,858 has almost the same structure as a Spindt-type field emission display (FED). The Spindt-type field emission structure is fabricated at the same time when a liquid crystal panel is fabricated, and thus its fabricating process is complex. Moreover, since the field emission structure is fabricated using semiconductor fabricating processes, its production cost is high and its production yield is low.